A typical repair valve is not a flanged structure that can allow depressurization of the structure surrounding an internal valve. Existing U.S. Pat. Nos. 3,908,691 and 6,983,759, for example, provide a “mother-valve” completely encompassing and containing a repairable or removable valve which is submerged in the pipeline fluid during its entire useful life. Such valves cannot easily use off-the-shelf pipeline control mechanisms, actuators and levers without providing complicated fluid tight seals between the “mother-valve” and the pipeline control mechanism because they are pressurized together.
An alternative valve is disclosed in U.S. Pat. No. 9,004,095. This valve connects two conduits with a support structure that can be opened to drain the structure's hollow through-passage by opening a port connected to the structure. This structure receives a gate with a selected valve and provides fluid communication between the first and second openings of the housing and is removably installed within the housing. However, this structure does not easily clear debris from the gate seating area, which can interfere with the valve's gate and body from seating in fluid tight engagement, and softer, corrosion resistant materials such as PVC, HDPE and composites are not ideal for use in this valve. There remains a need, therefore, for improved pipeline control valves.